Saws using two adjacent, circular saw blades are known from U.S. Pat. No. 963,520 to Costello. The two blades rotate round a common axis but in different directions which makes the sawing easier and the risk of sudden strokes smaller. A saw using only one blade in the form of a belt which cuts in both directions of travel is known from U.S. Pat. No. 822,056 to Knox. Again the advantage is that the sawing becomes easier and safer. It is also possible to arrange two belts running adjacent to each other but with different directions of travel.
A saw blade, which may be a circular disc or a belt depending on the machine, e.g. a twin blade cutter or a band saw, using it, usually consists of two materials. A first material, usually a mild steel, forms the body of the disc or belt. The cutting teeth of the saw blade are formed from a second material, usually a hard metal. The hard metal teeth are fastened to teeth holding necks formed on the mild steel disc or belt.
Since the two saw blades move in opposite directions or move in opposite rotational directions as the case may be, there is a certain risk that the teeth of one of the blades may hit and destroy the teeth of the other blade. The known solution to this problem is to introduce a thin spacer between the two saw blades. The spacer could be a separate detail or a projection on one of the saw blades holding the other saw blade at a desired distance. There is, however, still a certain risk that the teeth of one of the saw blades hit the teeth of the other saw blade, especially when the saw blades are exposed to a strain during the sawing. If the teeth hit each other they are usually destroyed which results in decreased sawing performance of the saw blade. There is also a certain risk that debris from the destroyed teeth may cause injury to the person operating the sawing machine.